Primordial non-Gaussianity in noncanonical warm inflation

Abstract

We study the bispectrum of the primordial curvature perturbation on uniform-density hypersurfaces generated by a kind of the noncanonical warm inflation, wherein the inflation is provided by a noncanonical scalar inflaton field that is coupled to radiation through a thermal dissipation effect. We obtain an analytic form for the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in first-order cosmological perturbation theory and analyse the magnitude of this nonlinear parameter. We make a comparison between our result and those of the standard inflation and the canonical warm inflation. We also discuss when the contribution to the non-Gaussianity due to the second-order perturbation theory becomes more important and what effect can be observed. We take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how the sound speed and the thermal dissipation strength to decide the non-Gaussianity and to get a lower bound of the sound speed constrained by PLANCK.Comment: 7 pages, 2 figure

Primordial non-Gaussianity in noncanonical warm inflation: Three- and four-point correlations

“…The analytic solutions of first and second order fluctuations, δφ 1 and δφ 2 , can be obtained by solving the two equations above. And then the non-Gaussianity generated by intrinsic non-Gaussian distributions of inflaton can be obtained [19], which we'll analyse concretely in next section.…”

“…Paper [19] researched non-Gaussianity in noncanonical warm inflation with a temperature independent dissipative coefficient preliminarily and yields:…”

Non-Gaussianity in a general kind noncanonical warm inflation

“…We concentrate on the extension of warm inflationary theory for years. At first, we construct the noncanonical warm inflation with a relatively simple Lagrangian density having separable form of kinetic and potential terms [18,39]. Then we extend warm inflation to the more general noncanonical field with a Lagrangian density having coupling form of kinetic and potential terms [40,41].…”

“…The non-Gaussianity in noncanonical warm inflation was first considered in the work [35] and it reached the conclusion that small sound speed and large dissipation strength can both enhance the magnitude of the non-Gaussianity. The studied case [35] is the noncanonical warm inflation with a Lagrangian density able to be written in a separable form for the kinetic term and the potential term. In this paper, the non-Gaussianity in a more general noncanonical warm inflation is calculated where the Lagrangian density can have a coupled form for the kinetic and potential terms.…”

Primordial non-Gaussianity in warm inflation using δNformalism

“…[22,[42][43][44]. The non-Gaussianity in noncanonical warm inflation was considered in [45] and find that small sound speed and large dissipation strength can both enhance the magnitude of the non-Gaussianity. About ten years ago, δN formalism was used to calculate the issue of non-Gaussianity for the first time [37,39].…”